The present invention is generally related to radio frequency (RF) signal couplers, and more particularly to a power detector with a matching impedance for RF signal amplifiers of cellular telephones.
In conventional cellular telephones, power detectors typically have been implemented by means of diode detectors (see U.S. Pat. Nos. 4,523,155 and 5,193,223). However, the sensitivity of such prior art diode detectors dictates the amount of coupling needed in order to detect low level signals. For example, in order to detect the lower power levels of RF signals produced by RF signal amplifiers of cellular telephones, 15 dB of coupling is needed. A 15 dB coupler typically has an insertion loss of 0.25 dB or more, representing a substantial amount of current drain that reduces battery talk time. For the, foregoing reasons, there is a need for an improved power detector that has enhanced detection sensitivity at low power levels.